Power train

ABSTRACT

Power train or an amphibious vehicle having an engine, transmission, and transfer case position in-line with longitudinal vehicle axis towards the rear of the vehicle, with transmission output facing the front of the vehicle. The transfer drive drives the rear wheels via propeller shaft, which extends adjacent the engine to rear differential. A marine drive PTO (power take off) may be taken from a shaft from the transfer case, from the propeller shaft, or from engine crankshaft pulley. Marine drive shaft may run below the engine, or alongside it, on the opposite side of the engine from propeller shaft. Decouplers may be provided to the PTO drive, to at least one rear wheel, and on the optional front axle propeller shaft.

BACKGROUND OF THE INVENTION

This invention relates to a power train which is particularly suitablefor use in an amphibious vehicle capable of travel on land and water,and more particularly to an adaptation of a conventional automotivepower train having an in-line engine and speed change transmission todrive both the rear wheels and the marine propulsion unit of anamphibious vehicle. The invention also relates to an amphibious vehiclehaving such a power train.

In a known automotive power train arrangement for a conventional landbased vehicle, an engine and speed change transmission are positioned atthe front of the vehicle in-line with the longitudinal axis of thevehicle. The driving end of the transmission faces the rear of thevehicle, and is connected by a drive shaft, otherwise known as apropeller shaft, to a rear differential for driving the rear wheels ofthe vehicle.

It is also known to use an in-line engine and speed change transmissionto drive the wheels and marine propulsion unit of an amphibious vehicle.For example U.S. Pat. No. 4,958,584 (Williamson) discloses a power trainarrangement in which the engine and transmission are located at the rearof the vehicle, with the driving end of the transmission facing thefront of the vehicle. A propeller shaft provides drive from thetransmission to a front differential for driving the front wheels of thevehicle. The rear wheels of the vehicle are not driven. A marinepropulsion unit is positioned behind the engine, and is driven from thetiming end of the crank shaft of the engine. This arrangement is bestseen in FIG. 5 of U.S. Pat. No. 4,958,584.

U.S. Pat. No. 4,838,194 (Williamson) is the parent application to U.S.Pat. No. 4,958,584 above. This patent also discloses an amphibiousvehicle having a power train arrangement in which an in-line engine andtransmission appear to be located at the rear of the vehicle, with thedriving end of the transmission facing the front of the vehicle. Thefront wheels are driven by a shaft from a transfer case which alsoprovides drive to a rearward facing marine drive.

The marine drive has a long propeller shaft to a screw propeller, bothof which, along with a rudder, can be raised for road use; and loweredfor marine use. The arrangement leaves little room anywhere in thevehicle for an engine and speed change transmission; the location ofwhich is not specifically disclosed.

If the engine and transmission are located behind the vehicle rear axle(as in the case in the continuation in part U.S. Pat. No. 4,958,584),they would either have to be located above the propeller shaft, raisingthe centre of gravity to the detriment of vehicle handling on land andwater; or to one side of the propeller shaft, giving odd weightdistribution, and packaging problems. Either of these options would needa skewed drive to the transfer box, leading to power losses and possibleNVH (noise, vibration, and harshness) problems. It should also be notedthat the long vertically adjustable propeller shaft would give rise tosealing problems in the bottom of the hull, which could lead to wateringress and corrosion problems in the transfer case. Altogether, thisdoes not appear to be a practical layout for an amphibious vehicle.

European patent No EP 0 341 009 (Royle) shows a further example of anamphibious vehicle in which an in-line engine and transmission areprovided at the rear of the vehicle, with the output of the transmissionfacing the front of the vehicle. In this layout, the transmission drivesthe rear wheels of vehicle via a drive shaft, whilst a marine propulsionunit, located behind the engine, is driven from the timing end of theengine.

There are significant disadvantages in the above known amphibiousvehicle power train arrangements, especially in the light of the highdemands which are required of a modern vehicle in road operation asdiscussed below.

When a vehicle accelerates in a forward direction, the front of thevehicle tends to lift upwards in reaction to the rotational accelerationof the wheels relative to the vehicle. This happens irrespective ofwhether the vehicle is front or rear wheel drive and can lead to a lossof traction between the front wheels and the road under acceleration.This problem is exaggerated in the known amphibious vehicle arrangementswhere the engine is positioned behind the rear wheels of the vehicle.This is because the weight of the engine when positioned behind the rearwheels adds to the lifting force; as opposed to a conventional powertrain arrangement with the engine at the front of the vehicle, where theengine weight would counteract the lifting force. Consequently, in theknown amphibious vehicle arrangements, the front wheels will tend tolose traction under acceleration. In practice this causes excessivewheel spin and tire wear. This is a particular problem in the Williamsonlayouts in which the vehicle is front wheel drive.

Furthermore, when a vehicle leaves a bend, the adhesion between the tyreand road surface must resist both acceleration and centrifugal forces.If the combination of these forces approaches or goes beyond thetractive limits of the front tyres, an under-steer condition will occur.In the conventional land based vehicle power train arrangementspreviously mentioned, the weight of the engine is positioned at thefront of the vehicle, which reduces the tendency to under-steer whencornering. However, in the known amphibious vehicle arrangements inwhich the weight of the engine is behind the rear wheels, there will bea reduction in the load on the front wheels which increases thelikelihood of under-steer occurring.

It is also known to provide for four wheel drive capability inconventional land based automotive vehicles having an in-line engine andspeed change transmission located at the front of the vehicle. In sucharrangements, the output end of the transmission faces the rear of thevehicle and a transfer case is used to selectively drive the rear wheelsonly or the front and rear wheels.

It has been proposed to use an automotive power train of this type todrive an amphibious vehicle, using the rear wheel drive to drive themarine propulsion unit and the front wheel drive to drive the frontwheels. In order to use the power train in this way, it is necessary tolocate the engine and transmission in the conventional position, towardsthe front of the vehicle.

Owing to rearward weight bias requirement for travel on water in anamphibious vehicle, it has been found unsuitable to locate the engineand transmission in this conventional position. It has also been found,contrary to the teachings in the Williamson patents, to be unsuitable todrive only the front wheels of an amphibious vehicle from a rear ormid-mounted engine, because the weight of the engine is not over thedriving wheels. This limits traction on wet slipways, leading toproblems leaving water; and can lead to wheel spin and rapid tyre wearon the road.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a power train for anamphibious vehicle in which a conventional in-line engine and speedchange transmission are utilised and in which the above disadvantagesare reduced or substantially obviated.

In accordance with a first aspect of the present invention, there isprovided a power train for an amphibious vehicle comprising an in-lineengine and speed change transmission assembly adapted such that theengine can be positioned towards the rear of the vehicle with thetransmission output facing the front of the vehicle, the power trainalso comprising a power take off means adapted to drive a marinepropulsion unit located behind the engine, characterised in that atransfer drive is provided in-line with the transmission, the transferdrive being adapted to drive the rear wheels of the vehicle via a firstdrive shaft which extends adjacent to the engine such that the enginecan be positioned at least partially forward of the rear wheels of thevehicle.

In a particularly preferred embodiment, the power train is adapted sothat the engine is mounted between the rear wheels and the front wheelsof the vehicle.

In one preferred embodiment the power take off is provided by thetransfer box which drives the marine propulsion unit by means of asecond drive shaft which runs substantially parallel to and below theengine. Alternatively, the second drive shaft could run substantiallyparallel to and along one side of the engine. In this latterarrangement, it is preferable if the first drive shaft runs along anopposite side of the engine to the second drive shaft.

In an alternative preferred embodiment, the power take off is driven bythe engine crankshaft at the timing end of the engine.

In a yet further alternative preferred embodiment, the power take offcomprises a further transfer drive which is fitted to, and driven by,the first drive shaft.

The marine propulsion unit may be a water jet, or a marine screwpropeller.

A decoupler may be provided in the drive line from the power take off tothe marine propulsion unit, to enable drive to the marine propulsionunit to be selectively coupled and decoupled.

Preferably, the first drive shaft is adapted to drive the rear wheels ofthe vehicle via a rear differential. Where a four wheel drive capabilityis required, the transfer drive can also drive a third drive shaft whichis adapted to drive the front wheels of the vehicle through a frontdifferential.

In an advantageous embodiment, a decoupler is provided in the drive linebetween the transmission and at least one of the driven road wheels,such that drive to the at least one driven wheel can be selectivelycoupled or decoupled.

Where a decoupler is provided for coupling drive to a wheel drive shaft,the decoupler may incorporate a synchromesh mechanism and may becombined with a constant velocity joint.

In accordance with a second aspect of the invention, there is providedamphibious vehicle having a power train in accordance with the firstaspect of the invention.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT

Several embodiments of the invention will now be described, by way ofexample only, with reference to the following drawings in which:

FIG. 1 is a perspective view of a first embodiment of a power train foran amphibious vehicle in accordance with the invention, in which a powertake off is connected to a crankshaft pulley of the engine;

FIG. 2 is plan view of the power train of FIG. 1;

FIG. 3 is side view, partially in section, of a modified form of thepower train of FIGS. 1 and 2;

FIG. 4 is a perspective view of a second embodiment of a power train inaccordance with the invention, in which a power take off is connected toa first drive shaft driving a rear differential of the vehicle; and

FIG. 5 is a plan view of the power train of FIG. 4;

FIG. 6 is a perspective view of a third embodiment of a power train foran amphibious vehicle in accordance with the invention;

FIG. 7 is a plan view of the power train of FIG. 6;

FIG. 8 is a side view, partially in section, of the power train of FIG.6;

FIG. 9 is a plan view of a fourth embodiment of a power train for anamphibious vehicle in accordance with the invention; and

FIG. 10 is a side view, partially in section, of the power train of FIG.9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Common reference numbers have been used throughout the drawings todenote parts in common between the different embodiments.

Referring firstly to FIGS. 1 to 3, a power train for use in anamphibious vehicle is generally indicated at 20, and includes alongitudinal power train assembly comprising an engine 8 and speedchange transmission or gearbox 9 arranged in-line with the longitudinalaxis of the vehicle A. The timing end 10 of the engine is locatedtowards the rear of the vehicle and the output from the transmissionfaces the front of the vehicle.

A transfer drive 13 is fitted in-line at the output end 11 of thetransmission 9 and transfers drive from the transmission 9 to acountershaft 14, the axis of which is offset relative to thelongitudinal axis A of the engine 8 and transmission 9. The countershaft14 is coupled to a first drive shaft 15, in the form of a propellershaft, which runs parallel to and along one side of the engine 8 todrive a rear differential 6. The differential 6 provides drive to theright hand side (as viewed in FIG. 1) rear wheel of the vehicle via arelay shaft 7 and a further drive shaft 12, whist the differential 6drives the left hand (as viewed) rear wheel via a drive shaft 18.

A decoupler or decouplers (not shown) may be provided in the drive linebetween the transmission and at least one of the driven road wheels toselectively decouple drive to the wheels when the vehicle is in marinemode. For example, a decoupler could be provided between the countershaft 14 and the first drive shaft 15. Alternatively, a decoupler ordecouplers could be provided between the differential 6 and one or bothof the rear wheels. In this latter arrangement, the or each decouplercould be provided between the differential 6 and a wheel drive shaft 12,18, or between a wheel drive shaft 12, 18 and its respective rear wheel.Where a decoupler is used to decouple drive to a wheel drive shaft 12,18, the decoupler may be of the type which incorporates a synchromeshmechanism and is combined with a constant velocity joint. Such adecoupler is disclosed in the applicant's co-pending U.S. 2004/0092175A1, the contents of which are hereby incorporated by reference.

A power take off for driving a marine propulsion unit 5 located behindthe engine is driven by the engine crankshaft at the timing end of theengine. In the present embodiment, the power take off is provided in theform of a coupling 1 which is fitted to, and is driven by, a crankshaftpulley 2 of the engine 8. The crankshaft pulley 2 being at the timingend of the engine 8. A second drive shaft 3 is connected at one end tothe coupling 1 and at the other end to a decoupler 4 which selectivelycouples and decouples drive from the second drive shaft 3 to the marinepropulsion unit 5. The marine propulsion unit may be a water jet ormarine screw propeller.

In circumstances where a pulley is not provided at the timing end of thecrankshaft, the power take off may be connected to the timing end of thecrankshaft by any suitable means. For example, the power take off couldbe connected to a sprocket provided at timing end of the crankshaft, orthe power take off may be connected directly to the timing end of thecrankshaft as appropriate.

In the arrangement shown, the relay shaft 7 which drives the right handrear wheel is located between the engine 8 and the marine propulsionunit 5. The relay shaft 7 can be positioned below the second drive shaft3, as shown in FIGS. 1 and 2, or above the second drive shaft 3, asshown in FIG. 3, depending on the vehicle layout.

Where a four wheel drive capability is required, the counter shaft 14can be connected to a third drive shaft 16 which drives the front wheels(not shown) via a front differential 17. A decoupler or decouplers (notshown) may be provided in the drive line between the counter shaft 14and the differential 17, or between the differential 17 and either orboth of the front wheels, in order that drive to the front wheels can beselectively coupled and decoupled.

A second embodiment of the invention will now be described withreference to FIGS. 4 and 5. An engine 8, transmission 9 and transferdrive 13 are arranged in the same manner as in the first embodimentdescribed above, with a first drive shaft 15 driving a rear differential6 from the transfer drive 13.

However, in this embodiment, the power take off is provided by a furthertransfer drive 22, which transfers drive from the first drive shaft 15to the second drive shaft 3 for driving a water jet 5. A decoupler 4selectively couples and decouples the drive from the second drive shaft3 to the water jet 5. The further transfer drive 22 transfers drive fromthe propeller shaft by means of a belt or chain, although it would bepossible to transfer the drive using gears.

One or more decouplers 24, 26 are provided in the drive line from thedifferential 6 to the rear wheels to allow selective decoupling of driveto the road wheels while the vehicle is in marine mode. In aparticularly preferred embodiment, the decouplers 24, 26 are providedinboard of CV joints 28 and 30 also provided in the drive line. Wherespace in the vehicle is at a premium, the decouplers 24, 26 could be ofthe type, discussed above, which incorporate a synchromesh mechanism andwhich are combined with a CV joint. In such an arrangement, the separateCV joints 28, 30 will not be required. As an alternative to providingdecouplers in the drive line between the differential 6 and the rearwheels, one or more decouplers may be incorporated into or ahead ofdifferential 6 or into the transfer drive 22.

Where a four wheel drive capability is required then this can beprovided in the same manner as has been described above in relation tothe first embodiment.

A third embodiment of the invention will now be described with referenceto FIGS. 6 to 8. The power train 50 comprises an engine 8 andtransmission 9 arranged in-line with the longitudinal axis of thevehicle. The engine is mounted toward the rear of vehicle with theoutput end 11 of the transmission 9 facing the front of the vehicle. Atransfer drive 13 is fitted to the output end 11 of the transmission 9and comprises a driving sprocket 18 which is drivingly coupled with anoutput shaft 42 of the transmission 9. The driving sprocket 18 isconnected in driving engagement by means of a drive belt 32 with a firstdriven sprocket 34, which is mounted to a first counter shaft 14, and asecond driven sprocket 36 mounted to a second counter shaft 37.

The first counter shaft 14 is connected via a decoupler 38 to a firstdrive shaft 15 which drives a rear differential 6. The rear differential6 with a relay shaft 7 is located at the rear of the engine 8 fordriving the rear wheels (not shown) of the vehicle.

The second counter shaft 37 is connected via a decoupler 40 to a seconddrive shaft 3. The second drive shaft 3 runs beneath the engine 8 to therear thereof, for connection to a marine propulsion unit 5, for examplea water jet.

As with the previous embodiments, a four wheel drive capability can beprovided by connecting the first counter shaft 14 to a third drive shaft16 for driving the front wheels via a front differential 17. As shown,the first counter shaft is connected to the third drive shaft 16 by adecoupler 41, so that drive to the front wheels can be selectivelycoupled and decoupled.

A fourth embodiment of the invention is shown in FIGS. 9 and 10. Thefourth embodiment is substantially identical to the third embodimentexcept that the second drive shaft 3, which drives the marine propulsionunit 5, is arranged to run along one side of the engine 8 rather thanbelow the engine. In the embodiment shown, the second drive shaft 3 runsalong the opposite side of the engine from the first drive shaft 15,alongside the lower part of the cylinder block, below the cylinder bank.This arrangement enables the engine to be positioned lower in thevehicle, resulting in a lower centre of gravity which improves thehandling characteristics of the vehicle in water and on land.

In a power train in accordance with the invention where the first driveshaft 15 is driven from the transmission through a transfer box, theaxis of the first drive shaft is offset relative to the longitudinalaxis of the engine 8 and transmission 9. Consequently, it is possible toposition the engine and transmission just in front of the rear wheelsand run the drive shaft 15 along one side of the engine to drive therear differential 6 and the rear wheels. This arrangement overcomes manyof the problems associated with the known amphibious vehicle power trainlayouts in which an in-line engine and transmission are located behindthe rear wheels. With the engine located just in front of the rearwheels, the weight of the engine and transmission help to counterbalance lift of the front of vehicle during acceleration. Furthermore,the centre of gravity of the vehicle is moved forward toward the centreof the vehicle, when compared with the prior art arrangements, whichimproves road holding and manoeuvrability of the vehicle on land.However, the engine and transmission are still located generally towardsthe rear of the vehicle which provides a more favourable weightdistribution for travel of the vehicle on water.

In alternative embodiments (not shown), the engine 8 could be mounted sothat only a part of the engine is located forward of the rear wheels.This may be advantageous in providing more room for passengers butwithout positioning the engine behind the rear axle as in the knownarrangements. However, it is advantageous if the whole engine is locatedbetween the front and rear wheels because then the engine can be mountedlower in the vehicle. This lowers the centre of gravity of the vehiclewhich improves vehicle handling as described above.

Whereas the invention has been described in relation to what arepresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not limited to thedisclosed arrangements but rather is intended to cover variousmodifications and equivalent constructions included within the spiritand scope of the invention. For example, it is not essential that drivebetween the power take off and the marine propulsion unit be connectedvia a decoupler. Furthermore, the first drive shaft 15 could be arrangedto extend beneath the engine 8 rather than along one side.

1. A power train for an amphibious vehicle comprising: an in-line engineand speed change transmission assembly adapted such that the engine canbe positioned towards the rear of the vehicle with the transmissionoutput facing the front of the vehicle; and a power take off meansadapted to drive a marine propulsion unit located behind the engine;wherein: a transfer drive is provided in-line with the transmission, thetransfer drive being adapted to drive a first drive shaft which extendsrearwardly along one side of, or beneath the engine and which is adaptedto drive a rear differential for driving the rear wheels of the vehicle,and the arrangement being such that the engine can be positioned atleast partially forward of the rear wheels, and wherein the drive forthe marine propulsion unit is provided through the transfer drive.
 2. Apower train as claimed in claim 1, adapted such that the engine can bepositioned between the rear wheels and the front wheels of the vehicle.3. A power train as claimed in claim 1, wherein the power take off isprovided by the transfer drive which is adapted to drive the marinepropulsion unit by means of a second drive shaft which runssubstantially parallel to and below the engine.
 4. A power train asclaimed in claim 1, wherein the power take off is provided by thetransfer drive which is adapted to drive the marine propulsion unit bymeans of a second drive shaft which runs substantially parallel to andalong one side of the engine.
 5. A power train as claimed in claim 4,wherein the first drive shaft runs along an opposite side of the engineto the second drive shaft.
 6. A power train as claimed in claim 1,wherein the power take off comprises a further transfer drive which isfitted to, and driven by, the first drive shaft.
 7. A power train asclaimed in claim 1 wherein the marine propulsion unit is a water jet, ora marine screw propeller.
 8. A power train as claimed in claim 1,wherein a decoupler is provided in the drive line from the power takeoff to the to the marine propulsion unit, to enable drive to the marinepropulsion unit to be selectively coupled and decoupled.
 9. A powertrain as claimed in claim 1 wherein the first drive shaft is adapted todrive the rear wheels of the vehicle via a rear differential.
 10. Apower train as claimed in claim 9, wherein the transfer drive alsodrives a third drive shaft which is adapted to drive the front wheels ofthe vehicle through a front differential.
 11. A power train as claimedin claim 1, wherein a decoupler is provided in the drive line betweenthe transmission and at least one of the driven wheels, such that driveto the at least one driven wheel can be selectively coupled ordecoupled.
 12. A power train as claimed in claim 11, wherein the atleast one decoupler is arranged for coupling drive to a wheel driveshaft, the decoupler incorporating a synchromesh mechanism and beingcombined with a constant velocity joint.
 13. An amphibious vehicle,characterised in that the vehicle comprises a power train as claimed inclaim
 1. 14. A power train for an amphibious vehicle comprising: anin-line engine and speed change transmission assembly adapted such thatthe engine can be positioned towards the rear of the vehicle with thetransmission output facing the front of the vehicle; and a power takeoff means adapted to drive a marine propulsion unit located behind theengine; wherein: a transfer drive is provided in-line with thetransmission, and the transfer drive is adapted to drive a first driveshaft which extends rearwardly along one side of, or beneath the engineand which is adapted to drive a rear differential for driving the rearwheels of the vehicle, the drive for the marine propulsion unit isprovided through the transfer drive, and the power take off comprises afurther transfer drive which is fitted to, and driven by, the firstdrive shaft, the arrangement being such that the engine can bepositioned at least partially forward of the rear wheels.